Dynamics of functionalized single wall carbon nanotubes in solution studied by incoherentneutron scattering experiments

Abstract

We have studied, by incoherent neutron scattering experiments, the dynamics of acolloidal suspension of functionalized single wall carbon nanotubes (SWNTs).The nanotubes have been functionalized with pentyl ester groups attached atthe ends and suspended in deuterated toluene with a concentration of 2.6 mgSWNT/1 ml of deuterated toluene. The experimental techniques were incoherent elastic neutron scattering(IENS) and incoherent quasielastic neutron scattering (IQNS). In the temperature rangebetween 4 K and 300 K, three phases were observed by IENS measurements: a solid phase forT<Tg, an undercooledliquid phase for Tg<T<Tm anda liquid phase for T>Tm. Furthermore, in the high temperature range of the undercooled liquidphase, hysteresis loops in the heating and cooling scans were observed. Thelower limit of the hysteresis loop defines the critical crossover temperatureTc. IQNS measurements in the liquid phase and a cooling scan of the undercooledliquid phase were performed. Three different quasielastic peaks were identified,two in the liquid phase and another one in the undercooled liquid phase. Thewidths of the quasielastic peaks are discussed as a generalized diffusion functionwhich can be factorized as a temperature dependent diffusion function and aQ dependent structure function. From the comparison of the diffusion function with theviscosity of toluene, we conclude that two components are in the long-time rangeBrownian motion and the other one in the short-time range Brownian motion.